Analysis of the Advantages and Disadvantages of Eddy Current Dynamometers

The electric eddy current dynamometer is an advanced loading measurement device mainly used to measure the mechanical performance of various power devices. It utilizes the eddy current effect to absorb the output power of the engine, featuring a small size, light weight, simple structure, low inertia, high precision, high stability, and convenient use and maintenance.

The electric eddy current dynamometer mainly consists of the rotor part (induction part), the swinging part (armature and excitation winding), and the fixed part. The rotor disc of the rotor part is connected to the prime mover via a coupling. When the prime mover rotates, it drives the rotor disc to rotate as well. During the rotation of the rotor disc, the magnetic flux density in the air gap changes periodically, inducing eddy currents. Due to the coupling effect of the 'eddy currents' and the magnetic field, a braking torque is generated on the rotor, while a torque equal to the drag torque is produced on the armature body. This torque is detected by a force sensor on the armature body, achieving the purpose of testing torque. For speed measurement, a non-contact magnetic-electric speed sensor is used to convert the speed signal into an electrical signal output.

The electric eddy current dynamometer not only has a fast response speed, high speed, and a wide power range, but also has good structural integrity, low inertia, good stability, and high precision, allowing for automated control and low operational difficulty. Therefore, it is widely used in the testing and development of internal combustion engines and performance tests, such as the development and testing of various types of internal combustion engines, quality monitoring of high-speed internal combustion engines, online testing and fatigue testing, fuel testing and lubricating oil testing for internal combustion engines, automotive wind resistance, simulation tests for gearboxes and rear axles, and complete transmission system simulation tests.

However, the electric eddy current dynamometer also has some drawbacks. Firstly, it cannot provide the test machine with the driving torque needed to complete related tests, nor can it recover the energy of the prime mover, which can only be consumed in the form of heat. Secondly, the two control loops of 'constant speed control' and 'constant current control' share a single regulator in the closed-loop control system, resulting in a smaller absorbed power. These drawbacks reduce the accuracy of constant speed control and constant torque control, while also limiting the actual application range.